XkbLookupKeySym is the equivalent of the core
XLookupKeySym function. For the core keyboard, given a keycode key and
an Xkb state state, XkbLookupKeySym returns the symbol associated with
the key in sym_rtrn and the list of modifiers that should still be applied
in mods_rtrn. The state parameter is the state from a KeyPress or KeyRelease
event. XkbLookupKeySym returns True if it succeeds.